Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.11.1 (protein kinase)
81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Enteroaggregative Escherichia coli (EAggEc) strains are associated with persistent diarrhea in children in the developing world and exhibit a classic aggregative phenotype. We have demonstrated that EAggEc strains isolated from children with persistent diarrhea in Brazil, Bangladesh, and Pakistan also have the potential to be internalized by HeLa cells in the gentamicin protection assay. We have confirmed this phenomenon with transmission electron micrographs of bacteria engulfed by HeLa cells. We examined the mechanisms by which this process occurs. Staurosporine inhibited internalization of EAggEc strain 162 by 50% at a concentration of 0.1 microM. Genistein inhibited internalization of this same organism by 50% at a concentration of 50 microM. Cytochalasin D inhibited internalization by 50% at a concentration of 1 microgram/ml. Staurosporine, genistein, and cytochalasin D inhibited the internalization of EAggEc strain 162 by HeLa cells in a dose-dependent manner. These data suggest that active cell processes such as signal transduction by protein kinase and/or tyrosine kinase may be involved in the internalization of EAggEc strain 162 by HeLa cells and that actin filaments and cytoskeletal structure may be important for this process.
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PMID:Characterization of an invasive phenotype associated with enteroaggregative Escherichia coli. 764 71

Congenital chloride diarrhea affects intestinal transportation of electrolytes, resulting in potentially fatal diarrhea. Linkage disequilibrium analyses have suggested the congenital chloride diarrhea gene (CLD) to lie within 0.37 cM from D7S496 in human chromosome 7q31. To clone the CLD gene, we have constructed and refined a physical map based on a 2.7-Mb YAC contig around D7S496 and identified two candidate genes. The physical positions of 4 known genes (DRA, PRKAR2B, LAMB1, DLD), 7 polymorphic repeat markers, and 13 CpG islands were established. DRA (down-regulated in adenoma) is expressed in the gut and encodes a protein with sequence homology to anion transporters, whereas PRKAR2B encodes a regulatory subunit for protein kinase A. Both genes map within 450 kb from D7S496, making them functionally and positionally relevant candidates for CLD.
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PMID:Positional candidate genes for congenital chloride diarrhea suggested by high-resolution physical mapping in chromosome region 7q31. 896 97

Stable toxin (ST) peptides are the causative agents for a severe form of watery diarrhea. These peptides bind to a membrane-associated form of guanylyl cyclase, guanylyl cyclase C. The result is an accumulation of cyclic guanosine monophosphate (cGMP) in the intestinal cell, regulating protein kinase activity and the phosphorylation of a number of proteins involved in ion transport across the intestine. Using the human T84 colonic cell line as a model system, we show that cGMP accumulation in these cells after ST application is regulated by the activity of the cGMP-binding, cGMP-specific phosphodiesterase (PDE5). The presence of human PDE5 in this cell line was confirmed by Western blot analysis, using an antibody raised to the bovine enzyme, and by the observation that cGMP hydrolytic activity detected in T84 cell lysates was almost completely inhibited by low concentrations of zaprinast, a specific inhibitor of PDE5. An increase in activity of PDE5 was observed in T84 cell lysates on exposure to the ST peptide and prolonged exposure of T84 cells to the ST peptide led to the induction of cellular refractoriness in these cells, which was largely contributed in terms of an increased rate of degradation of cGMP in desensitized cells as a result of PDE5 activation. This activation was correlated with an increase in the affinity of the enzyme for the substrate cGMP, as well as an increased affinity for zaprinast. We provide evidence for the first time that cGMP levels in the human colonocyte are regulated by the cGMP-hydrolytic activity of PDE5 and suggest that the expression and regulation of PDE5 in the intestine could therefore be important in controlling cGMP-mediated signaling in this tissue.
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PMID:Expression and regulation of the cGMP-binding, cGMP-specific phosphodiesterase (PDE5) in human colonic epithelial cells: role in the induction of cellular refractoriness to the heat-stable enterotoxin peptide. 1067 26

Infections with Shiga toxin (Stx)-producing bacteria cause bloody diarrhea which may progress to life-threatening complications, including acute renal failure and neurological abnormalities. The precise mechanism of disease progression is unclear, although evidence suggests that the localized production of the host proinflammatory cytokines tumor necrosis factor alpha (TNF-alpha) and interleukin-1 may exacerbate toxin-mediated vascular damage. Purified Stxs have been demonstrated to elicit proinflammatory cytokine synthesis from human peripheral blood mononuclear cells and monocytic cell lines in vitro. To understand toxin-monocyte interactions required for cytokine synthesis, we have treated differentiated THP-1 cells with purified wild-type toxins, enzymatic mutants, or B subunits and measured TNF-alpha production. Our data suggest that A subunit enzymatic activity is essential for cytokine production. THP-1 cells were treated with a series of protein kinase C (PKC), PKA, and protein tyrosine kinase inhibitors to examine the role of intracellular signaling molecules in Stx-mediated cytokine production. Treatment of cells with PKC and tyrosine kinase inhibitors blocked TNF-alpha secretion by Stx-stimulated THP-1 cells. Stx treatment directly activated PKC, which occurred at a point upstream of transcriptional activation of the gene encoding TNF-alpha.
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PMID:Shiga toxin-induced tumor necrosis factor alpha expression: requirement for toxin enzymatic activity and monocyte protein kinase C and protein tyrosine kinases. 1094 42

This review focuses on the clinical development of the prototype broad spectrum inhibitor of cyclin-dependent kinases (CDKs), flavopiridol, now undergoing Phase II single-agent trials and Phase I combination trials (with paclitaxel and cisplatin). Preclinically, flavopiridol is a potent inhibitor of CDKs 1, 2 and 4 in cell-free assays (IC(50)in the region of 100 nM) and tumour cell growth in vitro (typical IC(50)in the region of 100 nM). The drug showed in vivo antitumour activity (using iv., ip. or oral dosing) against a variety of human tumour xenografts, especially when administered on a regular daily, rather than weekly, schedule and most notably against prostate carcinoma, head and neck cancer, non-Hodgkin's lymphoma and leukaemia. The major toxicities observed in rodents were on the bone marrow and gastrointestinal tract. Pharmacokinetics were linear with dose and with a bi-exponential decline both in rodents and man. Oral bioavailability in rodents is in the region of 20%. Glucuronidation appears to be the major route of metabolism. Single-agent clinical trials have mainly used a 72 h continuous infusion schedule. Dose-limiting toxicities were diarrhoea and hypotension. Plasma concentrations in excess of those required for in vitro enzyme or cell growth inhibition are achievable. While there has been some evidence of single-agent antitumour activity (partial responses in a patient with renal cancer and another with gastric cancer), ongoing combination studies, especially with paclitaxel, where preclinical synergistic antitumour effects are observed, are promising. Doubt as to whether CDKs are the sole target responsible for the drug's antitumour effects have been raised by preclinical observations of apoptosis of non-cycling cells, effects on endothelial cells and non-CDK proteins, such as aldehyde dehydrogenase and glycogen phosphorylase, potent effects on PTEFb and transcription and its ability to directly interact with DNA.
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PMID:Flavopiridol, the first cyclin-dependent kinase inhibitor to enter the clinic: current status. 1109 60

Heat-stable enterotoxin (ST(a)) elaborated by E. coli is a major cause of diarrhea. The transmembrane protein guanylyl cyclase C (GC-C) is the acknowledged receptor for ST(a) and for the mammalian peptides guanylin and uroguanylin. Binding to GC-C results in generation of cGMP, activation of type II cGMP-dependent protein kinase, phosphorylation of CFTR and increased chloride and bicarbonate secretion. We had previously shown that ST(a) receptors (GC-C) are found on the brush border membranes of small intestinal enterocytes and of colonocytes. However, since it has subsequently been shown that the endogenous ligands for these receptors, guanylin and uroguanylin, circulate in blood, we proposed the existence of ST(a) binding sites on the basolateral membranes (BLM) of colonocytes. Specific binding of 125I-ST(a) to rat colonocyte BLM was seen. The kinetics of binding to the BLM were similar to binding to BBM. The nature of the BLM receptor is unknown. This suggests that circulating guanylin and uroguanylin, analogues of ST(a), may also function via the basolateral surface.
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PMID:Colonocyte basolateral membranes contain Escherichia coli heat-stable enterotoxin receptors. 1139 81

Guanylyl cyclase C (GC-C) was found to function as the principal receptor for heat-stable enterotoxins (STa), major causative factors in E. coli-induced secretory diarrhea. GC-C is enriched in intestinal epithelium, but was also detected in other epithelial tissues. The enzyme belongs to the family of receptor guanylyl cyclases, and consists of an extracellular receptor domain, a single transmembrane domain, a kinase homology domain, and a catalytic domain. GC-C is modified by N-linked glycosylation and, at least in the small intestine, by proteolysis, resulting in a STa receptor that is coupled non-covalently to the intracellular domain. So far two endogenous ligands of mammalian GC-C have been identified i.e. the small cysteine-rich peptides guanylin and uroguanylin. The guanylins are released in an auto- or paracrine fashion into the intestinal lumen but may also function as endocrine hormones in gut-kidney communication and as regulators of ion transport in extra-intestinal epithelia. They are thought to activate GC-C by inducing a conformational change in the extracellular portion of the homotrimeric GC-C complex, which allows two of the three intracellular catalytic domains to dimerize and form two active catalytic clefts. In the intestine, activation of GC-C results in a dual action: stimulation of Cl and HCO3 secretion, through the opening of apical CFTR Cl channels; and inhibition of Na absorption, through blockade of an apical Na/H exchanger. The principal effector of the GC-C effect on ion transport is cGMP dependent protein kinase type II, which together with GC-C and the ion transporters, may form a supramolecular complex at the apical border of epithelial cells.
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PMID:Structure and function of the heat-stable enterotoxin receptor/guanylyl cyclase C. 1195 98

The present studies were undertaken to determine the direct effects of nitric oxide (NO) released from an exogenous donor, S-nitroso-N-acetyl pencillamine (SNAP) on Cl-/OH- exchange activity in human Caco-2 cells. Our results demonstrate that NO inhibits Cl-/OH- exchange activity in Caco-2 cells via cGMP-dependent protein kinases G (PKG) and C (PKC) signal-transduction pathways. Our data in support of this conclusion can be outlined as follows: 1) incubation of Caco-2 cells with SNAP (500 microM) for 30 min resulted in approximately 50% inhibition of DIDS-sensitive 36Cl uptake; 2) soluble guanylate cyclase inhibitors Ly-83583 and (1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one significantly blocked the inhibition of Cl-/OH- exchange activity by SNAP; 3) addition of 8-bromo-cGMP (8-BrcGMP) mimicked the effects of SNAP; 4) specific PKG inhibitor KT-5823 significantly inhibited the decrease in Cl-/OH- exchange activity in response to either SNAP or 8-BrcGMP; 5) Cl-/OH-exchange activity in Caco-2 cells in response to SNAP was not altered in the presence of protein kinase A (PKA) inhibitor (Rp-cAMPS), demonstrating that the PKA pathway was not involved; 6) the effect of NO on Cl-/OH- exchange activity was mediated by PKC, because each of the two PKC inhibitors chelerythrine chloride and calphostin C blocked the SNAP-mediated inhibition of Cl-/OH- exchange activity; 7) SO/OH- exchange in Caco-2 cells was unaffected by SNAP. Our results suggest that NO-induced inhibition of Cl-/OH- exchange may play an important role in the pathophysiology of diarrhea associated with inflammatory bowel diseases.
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PMID:Modulation of Cl-/OH- exchange activity in Caco-2 cells by nitric oxide. 1218 Nov 76

Various signalling pathways can confer the malignant phenotype to a cell. Ras signalling proteins have been found to play an important role in controlling cellular growth. Raf-1 is a protein kinase that exerts its effects downstream of Ras in the mitogen-activated protein kinase pathway and is thus likely to be crucial in the development of the malignant phenotype. BAY 43-9006 is an orally administered selective inhibitor of Raf-1 and the first compound of its class to enter clinical trials. This article describes the early clinical data of BAY 43-9006 in patients with advanced, refractory solid tumours. To date, over 60 patients have been treated as part of four Phase I clinical trials. Dose levels have ranged from 50mg once weekly to 200mg twice-daily in continuous administration. The drug has been generally well tolerated with no dose limiting toxicity yet encountered. The more common toxicities have involved the gastrointestinal tract (diarrhea, nausea, abdominal cramping) and the skin (pruritus, rash, cheilitis). Pharmacokinetic evaluations have found BAY 43-9006 to have considerable interpatient variability. However, there seems to be an increase in C(max) and AUC values with increasing dose. There is no clear effect of food on bioavailability. Splitting the dose to twice-daily administration has shown increases in C(max) and AUC values but is also accompanied by considerable interpatient variability.
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PMID:BAY 43-9006: early clinical data in patients with advanced solid malignancies. 1236 52

An international meeting focused on farnesyl transferase inhibitors (FTIs) was held in Naples on 12 April 2002 and represented an excellent occasion to gather most of the clinicians who are involved in clinical trials with this class of new compounds. Oncogene mutations of the gene occur in approximately 30% of all human cancers and may have prognostic significance. Ras protein is normally synthesized as pro-Ras, which undergoes a number of post-translational modifications, among which farnesylation. Processed Ras proteins localize to the inner surface of the plasma membrane, and function as a molecular switch that cycles between an inactive and an active form. When in its active form, either because of the binding of an external ligand or because of its constitutive activation, Ras activates several downstream effectors, such as Raf-1, Rac, Rho and phospahtidylinositol-3 kinase, which mediate important cellular functions, such as proliferation, cytoskeletal organization and others. Interruption of the Ras signaling pathway can be basically achieved in three ways, i.e. inhibition of Ras protein expression through antisense oligonucleotides, prevention of Ras membrane localization and inhibition of Ras downstream effectors. SCH 66336 (lonafarnib; Sarasar), a tricyclic orally active FTI, has been the first of these compounds to undergo clinical development. The toxicity profile observed in all completed phase I/II trials has been fairly similar, since gastrointestinal tract toxicity (nausea, vomiting and diarrhea) and fatigue have generally qualified as dose-limiting toxicity (DLT). One objective response in a patient with pretreated non-small cell lung cancer (NSCLC) was observed. Based on preclinical evidence of synergism between lonafarnib and other anticancer agents, combination studies have been started. In particular, lonafarnib has been combined both with gemcitabine and with paclitaxel in phase I studies. Nausea, vomiting, diarrhea and myelosuppression represented DLTs in these studies, in which an encouraging clinical activity was observed, in particular in pancreatic carcinoma (lonafarnib plus gemcitabine) and in NSCLC (lonafarnib plus paclitaxel). R115777 (Zarnestra) is another novel orally active FT competitive inhibitor in clinical development. Single-agent phase I/II studies have shown that myelotoxicity and neurotoxicity are DLTs, intermittent schedule is probably better tolerated and antitumor activity is observed particularly in breast cancer. A number of combination studies with R115777 have been carried out; taken as a whole, they show that the drug can be easily combined with several anticancer agents and phase III trials exploring the potential benefit from incorporation of R115777 into active chemotherapy regimens are indicated. Two other FTIs are in an earlier stage of clinical development. BMS-214662 has the main advantage of being cytotoxic in nature, rather than cytostatic; in particular, potent antitumor activity in human tumor xenografts of different histologies has been reported. A major drawback for BMS-214662 is its severe gastrointestinal and liver toxicities, which prevent the achievement of adequate systemic exposures following the oral route. L-778,123 has been stopped in its clinical development due to its severe and unexpected toxicity, i.e. grade 4 thrombocytopenia and significant Q-T prolongation.
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PMID:Farnesyl transferase inhibitors: a major breakthrough in anticancer therapy? Naples, 12 April 2002. 1239 76


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